• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.6
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• pp.58-68
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• 2000

In this paper, a mathematical model of describing oxygen density in multi-band type reheating furnaces was presented. Model designed in this paper was composed of majorly two parts. One is a model regarding 'variation of existing gas'. The other is a model of showing 'variation of oxygen content'. Each model is designed by considering four factors related to variation of oxygen density based on chemical reaction, fluid dynamics and fuzzy theory. Four factors to be considered are combustion reaction in burner, fluid transfer between adjacent combustion bands, fluid transfer from furnace's inner space to external space, and input of external air via gates. According to simulation results, it was shown that varying pattern of oxygen density in each combustion band is similar to generally expected operation data in reheating furnace.

• Fisheries and Aquatic Sciences
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• v.12 no.3
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• pp.219-226
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• 2009

Seasonal variation in the biomass of eelgrass (Zostera marina) and epiphytic algae in two eelgrass beds (Dongdae and Aenggang Bay) around Namhae Island was investigated throughout 2005. Shoot density and eelgrass biomass differed across months and locations. Peak shoot density occurred from April to August 2005, whereas eelgrass biomass was higher in July and August 2005. Shoot density as well as eelgrass biomass were higher in Dongdae Bay compared to Aenggang Bay. A total of 21 epiphytic algal species (4 Chlorophyta, 2 Phaeophyta, and 15 Rhodophyta) were collected, and dominant species included Polysiphonia japonica, Lomentaria hakodantensis, Symphyocladia latiuscula, Champia sp., and Heterosiphonia japonica. Seasonal variation in both the species composition and biomass of epiphytic algae was substantial: peak epiphytic algal biomass occurred in January and December 2005. We also observed high epiphytic algal biomass in the eelgrass bed of Dongdae Bay. Seasonal changes in the biomass of eelgrass and epiphytic algae were primarily influenced by water temperature, whereas those of the epiphytic algal community were also correlated with eelgrass (substrate) morphology and growth, the life cycle of epiphytic algae, and physical characteristics within eelgrass beds. The spatial variation of eelgrass density and biomass were also limited by sediment characteristics.

• Korean Journal of Microbiology
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• v.20 no.3
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• pp.113-118
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• 1982

The distribution and annual variation of detergent-degrading bacteria which were isolated from the Han River downstream running through the center of Seoul area were studied. The concentration of dissolved detergent was the lowest, 2.16 ppm at site 1 and it was gradually increased to downstream, the highest, 2.67 ppm at site 4. Population density of detergent degrading bacteria was about $10^2{\sim}10^3 cells/ml$. The density of LAS degrading bacteria was 1.1 - 1.8 times larger than that of SDBS-degrading bacteria. In annual variation the lowest density was appeared on January and the highest on July. In seasonal distribution of LAS-degrading bacteria, annual dominant group was genus Pseudomonas. There were few except genus Pseudomonas in winter and the subdomiannt group in spring and summer was genus Aeromonas and Enterobacteriaceae respectively. In autumn genus Pseudomonas, Aeromonas and Enterobacteriaceae were equally distributed. In SDBS-degrading bacteria, the annual dominant group was also genus Pseudomonas.

• Journal of the Korean Vacuum Society
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• v.8 no.4A
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• pp.432-437
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• 1999

We have fabricated an in situ ellipsometer operating at He-Ne wavelength. It can be applied to the real-time, in-situ tracking of the ellisometric change which occurs during various sample treatments. As a rotating analyzer type, all optical elements and related parts are designed to share a common hollow-axis configuration, and hence the ellipsometer is compact in shape and simple in design. It is mountable on the spare ports of vacuum chamber with ease. Using this ellipsometer, we observed the effective density variation of previously grown $TiO_2$ thin films by using electron beam evaporation. The packing density of the as-grown film was 82%. When exposed to atomsphere, the micro-void of the film was filled with water vapor. This water-filled $TiO_2$ thin film was subject to heating/cooling cycles in vacuum and the ellipsometric variation versus temperature and cycling number was measured in real time using this in situ He-Ne ellipsometer.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1435-1438
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• 1994

The effects of Ge composition variation in $a-Si_{1-x}Ge_x:H$ alloy p-i-n solar cells on the physical properties and current density-voltage characteristics are analyzed by a new simulation modelling based on the update published experimental datas. The simulation modelling includes newly formulated density of gap density spectrum corresponding to Ge composition variation and utilizes the newly derived generation rate formulars which include the reflection coefficients and can apply to multijunction structures as well as single junction structure. The effects in $a-Si_{1-x}Ge_x:H$ single junction are analyzed through the efficiency, fill factor, open circuit voltage, short circuit current density, free carriers, trap carriers, electric field, generation rate and recombination rate. Based on the results analyzed in single junction structure, the applications to multiple junction structures are discussed and the optimal conditions reaching to a high performance are investigated.

• Journal of the Korean institute of surface engineering
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• v.39 no.3
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• pp.115-120
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• 2006

The codeposition behavior of WC particles from an additive-free nickel sulfate and sulfamate solution has been investigated. Electroplating of Ni/WC composites was carried out at different current density with variation of WC particle size. The Guglielmi adsorption mechanism is applied to the electroplating of the fine WC in Ni matrix. The contents of WC in Ni composite coating were increased both by increasing current density and WC concentration in the bath. The hardness of Ni/WC composite coating at low current density is higher than that at high current density since finer WC particles dispersed through the coating. The codeposition behaviors of Co coated WC particles were also investigated. Conducting layer of particles promoted the codeposition behavior of Ni/WC-Co composite coatings.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.5
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• pp.69-77
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• 2012

Relative density, used to express dynamics condition of sand quantitatively, is measured by RI Test, Standard Penetration Test and Cone Penetration Test. Each measurement method has demerits, which is complicated or needs a specific analysis instrument and an analysis of expert. Also the ground is in wet condition commonly because of an unsaturated zone between a saturated zone and a surface, so the behaviour of the ground has different engineering properties unlike the dry ground and it diminishes accuracy of measuring relative density. In this study, the correlation between relative density and penetration of fall cone test in dry condition and wet condition with variation of water content was analyzed and a simple measuring method for relative density was suggested. As a result, there were difference of penetration between dry sands and wet sands, the correlation between relative density and penetration showed linear expression and relative density could be measured by the linear relation.

• Journal of the Korean Geotechnical Society
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• v.34 no.1
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• pp.17-24
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• 2018

A buffer in a geological disposal system minimizes groundwater inflow from the surrounding rock and protects the disposed high-level waste (HLW) against any mechanical impact. As decay heat of a spent fuel causes temperature variation in the buffer that affects the mechanical performance of the system, an accurate estimation of the temperature variation is substantial. The temperature variation is affected by thermal and material properties of the system such as thermal conductivity, density and specific heat capacity of the buffer, and thus these factors should be properly included in the design of the system. In particular, as the thermal properties are variable depending on the density and water content of the buffer, consideration of the effects should be included in the analysis. Hence, in this study, a numerical model based on finite element method (FEM) which is able to consider the change of density and water content of the buffer was established. In addition, using the numerical model, a parametric study was conducted to investigate the effect of each thermal property on the temperature variation of the buffer.

• Journal of Energy Engineering
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• v.24 no.2
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• pp.1-8
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• 2015

Wax deposition hinders oil flow assurance. Huge amount of money and time were required for mitigation of wax deposition in the oil field. For prediction and mitigation of wax deposition problem, Wax Appearance Temperature(WAT), which is the temperature at which the first wax crystals start to form, needs to be measured in advance. There is a standard method which is optical way to measure the WAT of transparent oil. However, standard method cannot be applied to opaque oil which is common produced oil in the field. In this study, WAT of three transparent oil samples were measured using heat flux variation analysis, viscosity variation analysis and density variation analysis, and compared with WAT measured by standard method. As a result, WAT measured by density variation analysis is the more reliable than heat flux variation analysis and viscosity variation analysis. WAT of two opaque oils were measured using density variation analysis.

• The Research Journal of the Costume Culture
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• v.13 no.6 s.59
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• pp.896-909
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• 2005

In need of studies on the kinds and structure of thread, the biggest variable factor in knitwear patterns, this study attempts: to examine the physical properties by thread type to basically establish systematic data in order to utilize various mixture and structure of yarn and to contribute to the development of optical patterns by building a systemic and scientific methods to produce knit wear patterns though a statistical analysis of the relation between the variations and physical properties. The results is as follows: with time, a feature of knit, which causes instability making it difficult to maintain the original shape, related to material properties, the weight and expansibility recovery rate have the greatest influence on the variation of wale lengths, though the amount varies by material. The variation of course contraction is closely related to density, the dense fabrics showing the highest values, due to the bust of the human body, the wale length variation of the front is greater than that of the back, by a regression analysis of material properties and the variations is obtained showing the weight, density and expansibility recovery rate have the greatest influence on the wale extension and course contraction of knit.